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From: dik@zuring.uucp (Dik T. Winter)
Newsgroups: net.lang
Subject: Re: Cute little liar program (for hackers only)
Message-ID: <301@zuring.UUCP>
Date: Fri, 20-Jun-86 21:06:22 EDT
Article-I.D.: zuring.301
Posted: Fri Jun 20 21:06:22 1986
Date-Received: Wed, 25-Jun-86 06:32:47 EDT
References: <7772@watdaisy.UUCP>
Reply-To: dik@zuring.UUCP (Dik T. Winter)
Distribution: net
Organization: CWI, Amsterdam
Lines: 26
Apparently-To: rnews@mcvax

In article <7772@watdaisy.UUCP> mpdevine@watdaisy.UUCP writes:
>
>  During my CS340 lectures (a second course in Data Structures), I alluded to 
>some of the unusual features of some programming languages, in particular Pascal
>and Fortran.  On the spur of the moment (as an (spectacularly unsuccessful) 
>attempt at stimulating class participation), I suggested an exercise: write a 
>program which prints the identity of the compiler used to compile it.  In the 
>following script session, both liar.f and liar.p are links to the data file liar
>(which is the program in question). 
>
Reminds me.  Eons ago I wrote a program for the CDC Cyber which would be
compiled by 4 compilers (Fortran, Pascal, Algol 60 and Algol 68).
The most remarkable of the program was not that it passed 4 compilers,
but it reproduced itself (regardless of the compiler, however,  the
Algol 60 compiler choked because of some compiler restrictions).

This brings on another question.  Is it possible to create non-trivial
input to {t,d}itroff that reproduces itself?  (By non-trivial I mean
it should contain at least one line starting with period or apostrophe,
because, as a silly co-worker pointed out to me, the empty file
reproduces itself.  Also .sy should not be permitted.)
-- 
dik t. winter, cwi, amsterdam, nederland
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